Pin terminal electrode



June 28, 1960 H. c. FISCHER PIN TERMINAL ELECTRODE Filed June l2, 1959 JNVENToR. 5944 y 6 F/s rms/Q United States Patent O 1 Claim. (Cl. 1938-243) This invention relates .to an electrode, and more particularly to -a pin terminal electrode for tubular heating elements of such structural features that the cold endl thereof will withstand severe conditions of use and testsuch 4as a 2500 volts one second test, without short circuiting. The electrode construction of this invention is designed to withstand Itests and current surges such as above mentioned without short circuiting and provides an effective, durable construction useful for many industrial purposes such as, for example, for baseboard space heaters.

Examples of practical devices embodying the invention are described below and in the accompanying drawings; the invention is not limited thereto, but covers all other forms coming within .the scope or purview of the -disclosure herein.

In the drawings:

Fig. 1 is a fragmentary, longitudinal, sectional view of an electrode construction embodying the invention, showing the parts assembled prior to the step of compacting the powder within the outer tube, and

Fig. 2 is a similar View, after completion of the step, wherein the powder 15 is tightly compacted to complete the assembly procedure, showing the outer casing trimmed back from the plastic sleeve 14 to obtain over the surface distance required to meet the dielectric test.

The drawings illustrate the cold end of an electrode construction embodying the invention, comprising an elongated outer tube 10, which may be made of copper or other metal, proportioned to suit the speciiic use to which it is put; for example, one form found convenient is approximately one-fourth the size shown in the original drawings of this application; in .that form the dimensions .of the wall of the outer tube 10 are .315 x .032". 'I'he invention is not limited to dimensions, which arev exemplary only. An elongated electrode pin 11, which may be formed of mild steel, is positioned within the tube -10 and has one end 12 projecting partly out of the tube and beyond the free end 13 thereof. A high heat resistant, non-brittle dielectric sleeve 14 is positioned on the electrode pin 11 intermediate and spaced from the free end 20 of Ithe pin. Said plastic sleeve may be of Teflou, Kehl-T, or otherY high heatV resistant non-brittle dielectric material, and its wall dimensions, in the ex-V emplary :form above mentioned, may be of .146 x .015 wall thickness, -for example. The pin 11, in Ithe liner 14, is positioned within the elongated outer tube 10 so that the free end 13 of the outer tube will intersect the length of sleeve 14. The parts are assembled as shown in Fig. 1. The outer tube 10 is filled with a refractory powder 15 such as magnesium oxide, aluminum oxide or zirconium oxide which is then compacted by swaging or 2,943,290 Patented June 28, 1960 rolling to the compactness of hard rock to the free end 13 of the outer .tube 10, axially medially positioning the electrode E10 and its liner therein. The outer tube 10 and plastic sleeve 14 are trimmed to proper dimensions after compacting (as indicated in dotted lines, Fig. l). Electrical connection may be had from the other end 16 of the pin 11. A coil 17, which may be a nickel chromium wire, for example, is ixed to said end 1:6 of the electrode pin 1v1 as by providing the end 16 of the pin 11 with a reduced portion or with plurality of circumferential recesses 18` and positioning the end of the wire coil in said reduced portion or recesses. The wire coil may be welded to the end 16 of pin 11 as noted at 19 in the drawings.

The invention is designed and adapted lfor use as a termination electrode pin for tubular electric heating elements, used, for example, on high voltage air heaters, water heaters and baseboard heating elements. The

distance between the sheath and the electrode on such heating elements is very close and not normally capable of withstanding high voltages and high dielectric tests.

The construction above described and shown in the drawings is exemplary of the invention which may be carried out by other lforms suggested by the disclosure herein; all other forms coming within the scope and purview of the claim shall be deemed to be within the invention and covered thereby.

The device of the invention may be initially formed with the free end 13 of outer tube 110 and Ithe sleeve 14 in registry (as indicated in dotted lines in Fig. 1) and the powder 15v compacted therein as .above described, .following which the parts would be cut back to the full line form shown in Figs. v1 and 2. This procedure tacilitates accurate manufacture and makes allowance yfor any powder loss or .gap at the very remote end 21 of the device lfollowing the rolling operation, which would be eliminated in cutting the parts Iback to their full line form.

Having .thus described my invention, what I claim as new and desire to secure by Letters Patent is:

A pin terminal electrode for tubular heating elements having an elongated copper outer tube having a free end, an elongated mild steel electrode pin positioned within said tube and having one end projecting partly out of said tube, a sleeve of heat-resistant, non-brittle dielectric material of substantially less thickness than said tube positioned on said pin intermediate and spaced from the ends of said pin, said pin with lthe sleeve thereon being positioned within said elongated outer tube so that the sleeve will, intermediate its length, register with the free end of said outer tube, a refractory powder tightly compacted within the elongated outer tube to the hardness of rock, axially and medially to position the electrode pin on its sleeve therein, said refractory powder extending to the free end of Ithe elongated outer tube, the end of said pin interiorly of said tube being provided with a plurality of circumferential recesses, and a nickel chome wire coil having one end seated in said circumferential recesses and being welded to said pin.

References Cited in the le of this patent UNITED STATES PATENTS 2,546,315 Oakley Mar. 27, 1951 FOREIGN PATENTS 314,839 Great Britain July 3, 1929 

